Messages in this thread | | | Subject | Re: [PATCH] f2fs: fix long latency due to discard during umount | From | Chao Yu <> | Date | Thu, 26 Mar 2020 17:00:18 +0800 |
| |
Hi Sahitya,
On 2020/3/18 12:44, Sahitya Tummala wrote: > F2FS already has a default timeout of 5 secs for discards that > can be issued during umount, but it can take more than the 5 sec > timeout if the underlying UFS device queue is already full and there > are no more available free tags to be used. In that case, submit_bio() > will wait for the already queued discard requests to complete to get > a free tag, which can potentially take way more than 5 sec. > > Fix this by submitting the discard requests with REQ_NOWAIT > flags during umount. This will return -EAGAIN for UFS queue/tag full > scenario without waiting in the context of submit_bio(). The FS can > then handle these requests by retrying again within the stipulated > discard timeout period to avoid long latencies. > > Signed-off-by: Sahitya Tummala <stummala@codeaurora.org> > --- > v2: > - Handle the case where a dc can have multiple bios associated with it > > fs/f2fs/f2fs.h | 1 + > fs/f2fs/segment.c | 83 ++++++++++++++++++++++++++++++++++++++++++++++++------- > 2 files changed, 74 insertions(+), 10 deletions(-) > > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h > index 12a197e..67b8dcc 100644 > --- a/fs/f2fs/f2fs.h > +++ b/fs/f2fs/f2fs.h > @@ -340,6 +340,7 @@ struct discard_cmd_control { > struct list_head pend_list[MAX_PLIST_NUM];/* store pending entries */ > struct list_head wait_list; /* store on-flushing entries */ > struct list_head fstrim_list; /* in-flight discard from fstrim */ > + struct list_head retry_list; /* list of cmds to retry */ > wait_queue_head_t discard_wait_queue; /* waiting queue for wake-up */ > unsigned int discard_wake; /* to wake up discard thread */ > struct mutex cmd_lock; > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c > index fb3e531..4162c76 100644 > --- a/fs/f2fs/segment.c > +++ b/fs/f2fs/segment.c > @@ -1029,13 +1029,16 @@ static void f2fs_submit_discard_endio(struct bio *bio) > struct discard_cmd *dc = (struct discard_cmd *)bio->bi_private; > unsigned long flags; > > - dc->error = blk_status_to_errno(bio->bi_status); > - > spin_lock_irqsave(&dc->lock, flags); > + if (!dc->error) > + dc->error = blk_status_to_errno(bio->bi_status); > + > dc->bio_ref--; > - if (!dc->bio_ref && dc->state == D_SUBMIT) { > - dc->state = D_DONE; > - complete_all(&dc->wait); > + if (!dc->bio_ref) { > + if (dc->error || dc->state == D_SUBMIT) { > + dc->state = D_DONE; > + complete_all(&dc->wait); > + } > } > spin_unlock_irqrestore(&dc->lock, flags); > bio_put(bio); > @@ -1124,10 +1127,13 @@ static int __submit_discard_cmd(struct f2fs_sb_info *sbi, > struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info; > struct list_head *wait_list = (dpolicy->type == DPOLICY_FSTRIM) ? > &(dcc->fstrim_list) : &(dcc->wait_list); > - int flag = dpolicy->sync ? REQ_SYNC : 0; > - block_t lstart, start, len, total_len; > + int flag; > + block_t lstart, start, len, total_len, orig_len; > int err = 0; > > + flag = dpolicy->sync ? REQ_SYNC : 0; > + flag |= dpolicy->type == DPOLICY_UMOUNT ? REQ_NOWAIT : 0; > + > if (dc->state != D_PREP) > return 0; > > @@ -1139,7 +1145,7 @@ static int __submit_discard_cmd(struct f2fs_sb_info *sbi, > lstart = dc->lstart; > start = dc->start; > len = dc->len; > - total_len = len; > + orig_len = total_len = len; > > dc->len = 0; > > @@ -1203,6 +1209,14 @@ static int __submit_discard_cmd(struct f2fs_sb_info *sbi, > bio->bi_end_io = f2fs_submit_discard_endio; > bio->bi_opf |= flag; > submit_bio(bio); > + if (flag & REQ_NOWAIT) { > + if (dc->error == -EAGAIN) { > + dc->len = orig_len; > + list_move(&dc->list, &dcc->retry_list); > + err = dc->error;
I encounter lots of dmesg, which should be printed by __remove_discard_cmd()
F2FS-fs (dm-0): Issue discard(23552, 23552, 2) failed, ret: -11
This should happen only if we didn't handle all discard in 5 seconds during umount.
So I doubt we failed to move dc to retry_list, because after submit_bio(), end_io() is not called synchronously as the bio was just pluged?
Thanks,
> + break; > + } > + } > > atomic_inc(&dcc->issued_discard); > > @@ -1463,6 +1477,40 @@ static unsigned int __issue_discard_cmd_orderly(struct f2fs_sb_info *sbi, > return issued; > } > > +static bool __should_discard_retry(struct f2fs_sb_info *sbi, > + struct discard_policy *dpolicy) > +{ > + struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info; > + struct discard_cmd *dc, *tmp; > + bool retry = false; > + unsigned long flags; > + > + if (dpolicy->type != DPOLICY_UMOUNT) > + f2fs_bug_on(sbi, 1); > + > + mutex_lock(&dcc->cmd_lock); > + list_for_each_entry_safe(dc, tmp, &(dcc->retry_list), list) { > + if (dpolicy->timeout != 0 && > + f2fs_time_over(sbi, dpolicy->timeout)) { > + retry = false; > + break; > + } > + > + spin_lock_irqsave(&dc->lock, flags); > + if (!dc->bio_ref) { > + dc->state = D_PREP; > + dc->error = 0; > + reinit_completion(&dc->wait); > + __relocate_discard_cmd(dcc, dc); > + retry = true; > + } > + spin_unlock_irqrestore(&dc->lock, flags); > + } > + mutex_unlock(&dcc->cmd_lock); > + > + return retry; > +} > + > static int __issue_discard_cmd(struct f2fs_sb_info *sbi, > struct discard_policy *dpolicy) > { > @@ -1470,12 +1518,13 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi, > struct list_head *pend_list; > struct discard_cmd *dc, *tmp; > struct blk_plug plug; > - int i, issued = 0; > + int i, err, issued = 0; > bool io_interrupted = false; > > if (dpolicy->timeout != 0) > f2fs_update_time(sbi, dpolicy->timeout); > > +retry: > for (i = MAX_PLIST_NUM - 1; i >= 0; i--) { > if (dpolicy->timeout != 0 && > f2fs_time_over(sbi, dpolicy->timeout)) > @@ -1509,7 +1558,10 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi, > break; > } > > - __submit_discard_cmd(sbi, dpolicy, dc, &issued); > + err = __submit_discard_cmd(sbi, dpolicy, dc, &issued); > + if (err == -EAGAIN) > + congestion_wait(BLK_RW_ASYNC, > + DEFAULT_IO_TIMEOUT); > > if (issued >= dpolicy->max_requests) > break; > @@ -1522,6 +1574,10 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi, > break; > } > > + if (!list_empty(&dcc->retry_list) && > + __should_discard_retry(sbi, dpolicy)) > + goto retry; > + > if (!issued && io_interrupted) > issued = -1; > > @@ -1613,6 +1669,12 @@ static unsigned int __wait_discard_cmd_range(struct f2fs_sb_info *sbi, > goto next; > } > > + if (dpolicy->type == DPOLICY_UMOUNT && > + !list_empty(&dcc->retry_list)) { > + wait_list = &dcc->retry_list; > + goto next; > + } > + > return trimmed; > } > > @@ -2051,6 +2113,7 @@ static int create_discard_cmd_control(struct f2fs_sb_info *sbi) > for (i = 0; i < MAX_PLIST_NUM; i++) > INIT_LIST_HEAD(&dcc->pend_list[i]); > INIT_LIST_HEAD(&dcc->wait_list); > + INIT_LIST_HEAD(&dcc->retry_list); > INIT_LIST_HEAD(&dcc->fstrim_list); > mutex_init(&dcc->cmd_lock); > atomic_set(&dcc->issued_discard, 0); >
| |